Typically, within a service provider's IP Multimedia Subsystem (IMS) network, the network is not aware of the registration status of IP endpoints outside of the network. An enterprise, on the other hand, knows the registration status of endpoints within the enterprise, but does not have the capability of sharing this information, using the existing call signaling infrastructure. This limits the service provider to only providing SIP trunking solutions for local and long distance calling with the IMS. That is, the IMS network acknowledges these endpoints as always being registered, thus limiting the network in providing enhanced services like presence based routing to the enterprise and the endpoints therein.